Fibrillation potentials are a form of spontaneous muscle activity arising from single muscle fibers. The presence of these potentials are consistent with muscle denervation. The detection of fibrillation potentials can indicate underlying neuromuscular pathologies, including cervical or lumbosacral radiculopathies, entrapment neuropathies, demyelinating, polyneuropathies, or genetic or acquired myopathies.
Radiculopathies are diseases of the spinal nerve roots as they exit the spinal cord. They are most commonly caused by compressive processes such as intervertebral disc protrusion and degenerative osteoarthritis. Compressive radiculopathies of the lumbosacral and cervical regions are frequent and dangerous causes of lower back and neck pain, respectively. Back pain resulting from a radiculopathy is serious and may require surgery.
The detection of spontaneous muscle electrical activity is typically performed using needle electromyography (NEMG). This technique comprises inserting a needle electrode into the muscle of interest and passively observing the spontaneous bioelectrical activity. The bipolar concentric needle, the most commonly used needle electrode in clinical practice, records a differential signal at the tip of the needle referenced to either another needle electrode placed subcutaneously or a surface electrode. Insertion of the needle electrode results in a burst of electrical activity as the tip of the needle damages muscle fiber membranes, which quickly subsides once the needle ceases to move. In a fully relaxed, healthy muscle, there is no muscle generated bioelectrical activity.
The use of needle electromyography (NEMG) has several disadvantages. A typical electromyographic examination requires multiple needle insertions. The needle must be repositioned multiple times at each insertion point to ensure adequate spatial sampling of the muscle of interest. This procedure is consequently an invasive and painful method with a nominal risk of infection or bleeding. Furthermore, the procedure is expensive and cannot often be obtained for most patients unless the symptoms are severe and surgery is an immediate possibility. The invasive nature, cost and required expertise of NEMG limits its use to the late confirmation of suspected pathology and makes longitudinal patient monitoring impractical.
Conventional surface electromyography (SEMG) techniques are currently limited in their clinical use due to their lack of spatial resolution. SEMG techniques, in which the spectral characteristics of the signal are analyzed, are used to examine muscle fatigue as an indicator of neuromuscular pathology.